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This work explores the solvent extraction of precious metals, specifically rhodium and gold, from chloride solution, with the aims of understanding how existing extractants work and designing new extractants. A wide variety of analytical techniques are employed, demonstrating how they can be used together to assess extraction ability and provide insight into the identity of the extracted species. Computational techniques are also used; their implementation, often in conjunction with experiment, can identify the interactions which allow extraction to occur and explain differences in extraction behaviour. Chapter 3 focuses on understanding how amidoamine extractants interact with the Rh(III) complexes present in chloride solution and thus enable their extraction. Experimental analysis shows that at low concentrations of Rh(III), the extracted species is RhCl5(H2O).(LH)2, but at high concentrations a di-nuclear species, Rh2Cl9.(LH)3, is present in the organic phase and on aging an inner-sphere complex, RhCl3L, can form. The mode of extraction is found to differ from that of a simple amine-based extractant. Computational modelling explores the extraction behaviour of a series of amidoamine extractants, finding they have different anion binding modes depending on the number of intra-extractant hydrogen bonds they can form. This results in bis- and tris-amidoamines having a more suitable binding mode for the Rh(III) aquo-chloridometalate compared to a mono-amidoamine, which has a more suitable binding mode for chloride. Calculated formation energies are broadly in agreement with experimental results and suggest selectivity for [RhCl5(H2O)]2− over chloride is the source of the success of this class of extractants. This work presents a full mode of action analysis of the bis-amidoamine and rationalises why the amidoamine reagents were the first effective Rh(III) extractants from chloride solution: they are proton-chelating reagents, which can adopt a binding mode that is selective for larger, more charge-diffuse anions. Building on the work of Chapter 3, a theoretical screening study of other mono- and bisamidoamines (or amido-quaternary ammonium compounds) is presented in Chapter 4. Different potential binding modes of the molecules are explored computationally, and it is found that, where possible, N-H to anion binding is generally more favourable than intramolecule proton chelation and C-H to anion binding, with only one exception to this rule. Interestingly, this exception proves to have the most favourable energy of exchanging chloride for [RhCl5(H2O)]2−, suggesting that it would be the most effective at extracting the Rh(III) metalate. All other molecules are theoretically poorer extractants of Rh(III) and, based on a comparison of the energies of formation, it appears that the reason for this is less favourable association with [RhCl5(H2O)]2−, more favourable association with chloride, or a combination of the two. This work highlights the importance of a favourable C-H to anion, or "soft", binding mode in the selective extraction of Rh(III) metalate over chloride, and how small structural changes to the extractant can drastically alter the favourability of this type of binding mode. Chapter 5 explores the possibility of using polyamine-based Rh precipitants or reagents based on them for Rh extraction. It is found that "precipitant" molecules with long chain Rgroups added are capable of extracting Rh(III) metalate very well, even from solutions of high HCl concentration. At high HCl concentrations, the most likely Rh(III) species extracted from the aqueous phase is [RhCl6]3−, with which the extractant is expected to associate in the outer-sphere. In contrast, it is found that an inner-sphere complex forms upon extraction from solutions of very low chloride concentrations. Extraction from mixed Rh(III)/Pt(IV) aqueous solutions is also investigated, but no selectivity for Rh(III) over Pt(IV) is found. Rh(III) stripping from the loaded organic is investigated using a number of reagents, with ammonium hydroxide solution found to be the most effective. The reagent designed and tested has the potential to be used for the solvent extraction of Rh industrially, offering extraction at the higher HCl concentrations typically used in existing metal recovery flowsheets. Industrially, Au(III) solvent extraction from chloride solution is well established, however, some of the reagents used are still not well understood. Chapter 6 aims to explain the extraction mechanism, and particularly the role of water, in Au(III) recovery with an industrial reagent via classical molecular dynamics simulations, which allow the assembly of the extracted species to be viewed and analysed. Experimental conditions can be modelled, but, in addition, so can other, non-experimental conditions to permit a better understanding of the extraction behaviour. Analysis of the output structures suggests that water's primary role in extraction is as the positive charge carrier. In some systems, where chloride is considered as the anion, the water partially hydrates the extracted anion, acting as a mediating agent between the electronegative functional groups on the extractant and the anion. This new insight into the nature of the extraction assemblies provides a greater understanding of the role of water in the extraction mechanism, and the means by which the extractant transports [AuCl4]‒ into the organic phase, information which can be used for informed modification of existing extraction processes and development of new reagents.

This thesis describes the development of gold, rhodium and palladium complexes incorporating a series of fluorinated N-heterocyclic carbene (NHC) ligands (NHC = 1,3-bis(fluorophenyl)imidazol-2-ylidene, fluorophenyl = 4-fluorophenyl (NHC-1), 2,4-difluorophenyl (NHC-2), 2,6-difluorophenyl (NHC-3), 2,4,5-trifluorophenyl (NHC-4) and 2,4,6-trifluorophenyl (NHC-5) and examines their steric and electronic properties and catalytic activities. The electronic properties have been evaluated by investigating the 77Se NMR chemical shifts of the corresponding selenium adducts, Se(NHC-1), Se(NHC-2), Se(NHC-3), Se(NHC-4) and Se(NHC-5). Comparative studies revealed that the fluorinated NHC ligands have stronger π-accepting abilities than the non-fluorinated NHC counterparts, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) and 1,3-bis(phenyl)imidazol-2-ylidene (IPh). The novel gold(I) complexes featuring fluorinated NHC ligands, [AuCl(NHC-1)] (Au-1), [AuCl(NHC-2)] (Au-2), [AuCl(NHC-3)] (Au-3), [AuCl(NHC-4)] (Au-4) and [AuCl(NHC-5)] (Au-5) have been synthesised and employed in the A3 coupling reaction of benzaldehyde, dibenzylamines and phenylacetylene. The catalytic activities of these complexes increased in the order of increasing steric bulk and π-accepting abilities of the NHC ligands. The preparation of the rhodium(I) complexes bearing fluorinated NHC ligands, [Rh(cod)Cl(NHC-1)] (Rh-21), [Rh(cod)Cl(NHC-2)] (Rh-22), [Rh(cod)Cl(NHC-3)] (Rh-23), [Rh(cod)Cl(NHC-4)] (Rh-24) and [Rh(cod)Cl(NHC-5)] (Rh-25) is reported. The catalytic activities of Rh-21, Rh-22, Rh-23, Rh-24 and Rh-25 in the transfer hydrogenation of acetophenone to 1-phenylethanol were exceptionally higher than non-fluorinated derivatives, [Rh(cod)Cl(IPh)] (Rh-26) and [Rh(cod)Cl(IMes)] (Rh-27). The new palladium(II) complexes containing fluorinated NHC ligands, [Pd(NHC-1)(3-Cl-pyridyl)Cl2] (Pd-21), [Pd(NHC-2)(3-Cl-pyridyl)Cl2] (Pd-22), [Pd(NHC-3)(3-Cl-pyridyl)Cl2] (Pd-23), [Pd(NHC-4)(3-Cl-pyridyl)Cl2] (Pd-24) and [Pd(NHC-5)(3-Cl-pyridyl)] (Pd-25) have been prepared and tested in the Suzuki-Miyaura coupling of phenylboronic acid and 4-iodotoluene. All these complexes have better catalytic performance than those of the non-fluorinated counterparts, [Pd(IMes)(3-Cl-pyridyl)Cl2] (Pd-14) and [Pd(IPh)(3-Cl-pyridyl)Cl2] (Pd-26). The findings from this work suggest that the presence of fluorine in NHC ligands affects the steric and electronic properties and enhances the metal complexes catalytic activities in various organic reactions. The link between the steric and electronic properties of the fluorinated NHCs and the outcome of the reactions in each catalytic system was investigated and reported in this thesis.

The work in this thesis aims to develop new systems for the more efficient recovery of metals from aqueous solution using solvent extraction. Understanding the underlying coordination chemistry to improve hydrometallurgical methods is crucial in order to meet the demand for critical metals for use in modern technologies, reduce the environment impact of recovery from primary mining deposits, and recycle valuable metals from secondary sources (e.g. mobile phones, WEEE). Chapter 2 examines the use of a simple primary amide that can load gold and other chloridometalates into a toluene phase through an outer-sphere mechanism. The loading of a variety of metals/metalloids from varying [HCl] is reported, highlighting the selectivity for gold over other metalates and chloride due to a combination of speciation of those metals and the relative ease of extraction of lower charged species (the Hofmeister bias). The advantages in loading/stripping, toxicity and mass balances compared to commercial alternatives are also outlined, in particular the efficacy of separating gold from a mixed-metal solution representative of those found in WEEE. The mode of action of the primary amide (and secondary/tertiary analogues) is determined using slope analysis, Karl-Fischer water determinations, NMR and MS measurements, EXAFS and computational models. The extraction occurs by the dynamic assembly of multiple amide ligands and gold metalates to generate supramolecular clusters held together through hydrogen-bonding and electrostatic interactions. The secondary and tertiary amides are found to be able to extract monoanionic metalates in a similar manner as the primary amide, although clustering occurs to a lesser extent. Whilst the secondary and tertiary amides are stronger gold extractants than the primary amide, they are not observed to be as successful when extracting from a mixed-metal solution. Instead, a 3rd phase is seen to form from these amides and some metals at higher metal concentrations, which removes the ligands from solution and prevents successful extraction of gold. Chapter 3 builds on an observation in Chapter 2 that a synergistic combination of a simple primary amide and an amine can extract chloridometalates that are typically difficult to solvent extract, such as iridium(III) and rhodium(III). These metalates, complexes with increased anionic charge and varying speciation in aqueous solution, are typically recovered last in a metal production flowsheet. The combination of a primary amide and primary amine was found to be the most effective at extracting the chloridometalates; the strength and strippability of the system is of particular interest in the context of rhodium(III) recovery as this metal currently is not extracted in commercial circuits. The mode of action of the system is investigated using similar techniques to Chapter 2, and reveals that the amine is the more important component of the synergistic mixture compared to the amide, with an improvement in extraction observed when both components are present. Rh(III) is extracted as a mixture of RhCl6 3– and RhCl5(OH2)2– complexes, dependent on the initial [HCl] concentration and the age of the initial aqueous solution. Chapter 4 investigates the feasibility of the recovery of lanthanides as anionic metalates from chloride-, nitrate- or sulfate-rich feeds. Reagents that have been found to be strong chloridometalate extractants, fragmented versions of these, and ‘classic’ commercial outer-sphere reagents are studied. The variations of ligand, anion type and concentration, proton concentration and solvent for the extraction of lanthanides is investigated. However, despite these permutations, no extraction of lanthanides is observed due to the difficulty in extracting more highly hydrated species and the lack of stability of the metalates in aqueous solution.

The main goal of this work was to understand factors affecting the rate of catalytic enamine hydrogenation, define promising chiral ligand scaffolds to perform the reaction enantioselectively, to prepare new efficient catalysts and to understand the reaction mechanism. Enamines were prepared by three different routes, one of which is a regio-selective intramolecular hydroaminovinylation of an amine-functionalised alkene. Achiral phosphorous ligands were tested in hydrogenation of these enamines. It was shown that electron-withdrawing ligands are beneficial in the reaction. Steric bulk within the ligands or the substrates also results in higher productivity. Electron-deficient phosphine ligands were able to perform hydrogenation of enamines with tetrasubstituted double bonds, which, to the best of our knowledge, have never been described in the literature. An unprecedented TON of up to 4550 mol mol-1 was achieved with one of the substrates. Hydrogenation of the enamines with chiral PHANEPHOS (in this project, 4,12-bis(di-aryl-phosphino-[2.2]-paracyclophane) ligands revealed that the electronic effect in the rhodium-catalysed hydrogenation of enamines is also of a paramount importance when chiral bis-phosphine ligands are used. The beneficial effect of iodine as co-catalyst is described. Addition of I2 improves both the rate of the reaction, as well as the ee of the product, exerting a dramatic effect in boosting the latter. An electron-deficient PHANEPHOS / Rh catalyst in the presence of I2 is able to hydrogenate even enamines with tetrasubstituted double bond. Chiral phospholane complexes of rhodium (complexes of chiral BPE (bis-(phospholanyl)ethane) (e.g. (+)-{1,2-Bis[(2R,5R)-2,5-diethylphospholan-1-yl]ethane}(cycloocta-1,5-diene)rhodium(I) tetrafluoroborate) and DuPhos (bis-(phospholanyl)benzene) (e.g (-)-{1,2-Bis[(2S,5S)-2,5-diethylphospholan-1-yl]benzene(cycloocta-1,5-diene)rhodium(I) tetra-fluoroborate) were also explored in this study. The use of an iodine co-catalyst proved to be very useful with the Rh / phospholane catalysts as well: addition of it resulted not only in the improvement of the rate of the reaction and increase in the enantioselectivity, but also caused the inversion of the absolute configuration of the product. An especially dramatic enantioselectivity switch was observed when chlorobenzene was used as a solvent. Mechanistic studies revealed that the enamine hydrogenation in the presence of a phospholane / Rh catalyst and iodine proceeds via the formation of the iminium ion, followed by the reduction of it with metal hydride. The actual catalyst is proposed to be a fairly acidic [Rh(ligand*)I2(H2)]+ complex.

Rhodium-catalysed enantioselective allylation reaction of imines in the presence of chiral diene ligands has been investigated. Under the optimised conditions, cyclic imines provided homoallylic amines in high yield and excellent enantioselectivities. The reaction most likely proceeds via allylrhodium(I) intermediates, and represents the first rhodium-catalysed enantioselective nucleophilic allylation of π-electrophiles with allylboron compounds. Furthermore, the allylations display a strong preference for carbon–carbon bond formation at the more substituted terminus of the allyl fragment of the allyltrifluoroborate. To demonstrate the utility of the allylation products, representative manipulations were conducted. Enantioselective Nickel-Catalysed Michael Additions of 2-Acetylazaarenes to Nitroalkenes An enantioselective Michael addition of acylazaarenes with α-substituted β-nitroacrylates in the presence of a chiral Ni(II)–bis(oxazoline) complexes has been developed. A range of azaaryl nucleophiles were shown to react with a variety of nitroalkenes to construct highly functionalised Michael addition products which contain a stereogenic all-carbon quaternary stereocentre with moderate to high yields and enantioselectivities. A possible mechanism for this reaction has been proposed.

A highly enantioselective and diastereoselective rhodium-catalysed addition of potassium allyltrifluoroborates to cyclic imines is described within. By utilising rhodium-chiral diene complexes, a wide range of cyclic imines were successfully allylated in high yields and enantioselectivities. Using a variety of more highly substituted allyl reagents, additional stereocentres and further molecular complexity was achieved with good yields, enantioselectivities and diastereoselectivities. Investigations involving isomeric allyl species and deuterated allyl species provided results that gave mechanistic insight, leading to the proposal of a plausible mechanistic pathway and suggested the formation of interconverting allylrhodium intermediates. Furthermore, during these investigations, a highly interesting isomerisation of the allylrhodium intermediate was discovered. Such isomerisation led to the in situ formation of the more complex allylrhodium intermediates which led to complex products upon allylation with cyclic imines that would be difficult to synthesis via other methods. This isomerisation was found to occur for a range of cyclic imines and disubstituted allyltrifluoroborates, proceeding in good yields and diastereomeric ratios. Deuterium studies indicate it is probable that this isomerisation proceeds via a 1,4 rhodium migration and a plausible mechanism is proposed explaining both the connectivity of the products and the relative stereochemistry.

This thesis explores the reactivity of amine-boranes with the {Rh(Xantphos)}+ fragment, with the aim of gaining mechanistic insight into the catalytic dehydropolymerisation of the amine-borane H3B∙NMeH2 to yield the polyaminoborane [H2BNMeH]n. Chapter 2 describes the synthesis of suitable RhIII and RhI Xantphos precursors to be used in this investigation. Moreover, the first example of the dehydrogenative B—B homocoupling of the tertiary amine-borane H3B∙NMe3 to form H4B2•2NMe3 is reported. The synthesis of the RhI precatalyst introduced in Chapter 2 entails the hydroboration of tert-butylethylene by H3B∙NMe3. In Chapter 3, the ability of the {Rh(Xantphos)}+ fragment to mediate this hydroboration in a catalytic manner is explored, and a mechanism is presented in which reductive elimination is proposed to be turnover-limiting. Other alkenes and phosphine-boranes are also trialled to determine the scope of the hydroboration. Chapter 4 investigates the catalytic dehydrocoupling of H3B∙NMe2H and H3B∙NMeH2 with {Rh(Xantphos)}+ to form the dehydrocoupling products [H2BNMe2]2 and [H2BNMeH]n, respectively, and the dehydrocoupling mechanisms are shown to be similar. Both involve an induction period in which the active catalyst is formed (thought to involve N—H activation), and saturation kinetics operate during the productive phase of catalysis. H2 is shown to inhibit the dehydrocoupling, and lead to production of shorter chain [H2BNMeH]n. Conversely, using THF as the dehydropolymerisation solvent instead of C6H5F results in longer chain [H2BNMeH]n. Finally, Chapter 5 presents new dicationic {Rh(Xantphos)}-based dimers, the formation of which involves loss of a phenyl group from the Xantphos ligands by P—C activation. The dimers are produced by routes involving either dehydrogenative homocoupling of H3B∙NMe3, or dehydrocoupling of H3B∙NMe2H. One of these dimers was tested as a catalyst for the dehydrocoupling of H3B∙NMe2H, and the reaction kinetics appear closely related those obtained using {Rh(Xantphos)}+, suggesting that the active catalysts in each system may be related.

Catalysis plays a key role in chemical conversions by making them faster and more selective. Despite its widespread use and decades of academic and industrial research, limited catalyst selectivity and stability still call for major improvements in catalyst performance to meet the demands of a sustainable society. Phosphine ligands are ubiquitous in transition metal chemistry and lead to extremely reactive and versatile homogeneous catalysts. Fast development of tailor-made catalysts and catalyst recovery are key issues in (asymmetric) homogeneous catalysis. Therefore libraries of ligands have to be synthesised and screened in an efficient way, which could be facilitated by Solid Phase Synthesis (SPS). Currently, most polymer bound ligands are anchored to the support after the synthesis in solution. However, the main advantages of synthesising the ligands directly on the polymeric support are not only easy catalyst recycling and product separation, but also the ease of purification during the synthesis steps, namely by simple washing and filtration. The use of SPS is very efficient for high throughput synthesis and screening of ligand libraries, however applications of SPS towards libraries of phosphorus ligands are rare, because the synthetic methodologies are still lacking. Here we present the development of methodologies towards novel immobilised bis(phosphine) ligands synthesised on polystyrene and JandaJel™ resin. By performing the synthesis steps on a solid support, the advantages of SPS are fully utilised. Successful routes have been developed towards immobilised secondary phosphine-boranes, which were versatile synthons to prepare a variety of new polymer-supported (C-chiral) bis(phosphine) ligands. These ligands were then tested for their catalytic activity in rhodium catalysed hydrogenation reactions.

This thesis discusses the intermolecular hydroacylation reaction using cationic rhodium bis- phosphine complexes as catalysts. A series of small bite-angle rhodium bis-phosphine complexes have been prepared and characterised. The reactivity of these complexes has been investigated in order to gather information about the effect of subtle changes in the ligand design and they are compared to the previously reported catalysts. Chapter 2 presents the challenges involved in the synthesis of small bite-angle isopropyl and cyclohexyl PNP and PCP bis-phosphine ligand containing rhodium complexes. These complexes have been fully characterised and screened in intermolecular hydroacylation reaction using 2- (methylthio)benzaldehyde (E) and 1-octene or 1-octyne as substrates. The formed complexes were shown to be very efficient and regioselective alkyne hydroacylation catalysts. The mechanism of the hydroacylation reaction was investigated using the isopropyl PNP complex [Rh(iPrPNMePiPr2)(C6H5F)][BArF4] (11b). Chapter 3 concentrates on developing new rhodium bis-phosphine complexes that involve a ligand incorporating the small bite-angle motif with the one of hemilability. The PNP complex [Rh((2-OMe-C6H4)2PNMeP(2-OMe-C6H4)2)(C6H5F)][BArF4] (41) was synthesised and analytically characterised. 41 was shown to be an active alkyne hydroacylation catalyst with more stability towards the catalyst deactivation pathway, reductive decarbonylation, compared to the previously investigated 11b. Additionally mechanistic studies using 41 were carried out. The final chapter moves on to study the C-S activation ability of small bite-angle rhodium bis- phosphine complexes to remove the sulfur tether from the hydroacylation products at the end of the hydroacylation reaction. A screening is conducted to compare the reactivity of different small bite-angle ligands. Additionally, a detailed investigation is carried out to see the effect the C-S activation has on the hydroacylation reaction.

This thesis describes the synthesis and characterisation of a series of cationic rhodium bis-phosphine complexes. The reactivity of these new complexes in the solid-state and in solution is reported. In Chapter 2 the synthesis of a series of rhodium bis-phosphine diene complexes is presented and the reactions of these complexes with hydrogen in the solid-state are investigated. Several examples of zwitterionic complexes coordinating the [BArF4]─ anion are produced by hydrogenation. A rare example of a sigma-alkane complex, [Rh(iBu2PCH2CH2PiBu2)(eta2-CH-eta2-CH-NBA][BArF4]^{─iBu2PCH2CH2PiBu2)(eta2-CH-eta2-CH-NBE][BArF4] may form as a short lived intermediate prior to the formation of the sigma-alkane complex. The temporal evolution of the solid-state hydrogenation reactions is monitored by powder X-ray diffraction methods. In Chapter 3 the C−X activation of various aryl halides using the [Rh(iBu2PCH2CH2PiBu2)]+ fragment is reported. The 'ligand innocence' of the phosphine with respect to intramolecular C−H activation is also discussed. A rare example of C−X activation in the solid-state is presented, which shows the formation of an isomer that is not observed by analogous solution routes. Chapter 4 investigates solid-state ligand exchange reactions using ethene, butadiene, CO and NH3 gases. A solid-state transfer dehydrogenation reaction is reported within single crystals of [Rh(iBu2PCH2CH2PiBu2)(C2H4)2][BArF4]. H/D exchange of NH3 can also occur in the solid state in the bis-ammonia complex [Rh(iBu2PCH2CH2PiBu2)(NH3)2][BArF4]. A variety of rhodium complexes are tested as heterogeneous catalysts for the hydrogenation of ethene and the isomerisation of butene. In Chapter 5 the binding affinity of a variety of fluorinated arenes to rhodium bis-phosphine fragments is presented using ESI-MS methods. The dependence upon the arene substituents, phosphine substituents and phosphine bite angle are discussed.}

The interest in biosensors can be attributed to the first described enzyme containing sensor used to detect levels of glucose in 1962. Although research into biosensors was initially slow to pick up, the field has become increasingly popular and research has been widespread for the last 20 years. The continuing research into biosensors is crucial as this will improve current devices to become smaller, faster and more economical and yield new biosensors. This thesis is mostly concerned with the development of an integral component of a biosensor, the redox mediator. Complexes of ruthenium incorporating electron rich sulfur-donor ligands such as naphthalenedithiol should possess interesting redox qualities which could be used to produce better mediators. A second area covered in this thesis is in the structural studies of a series of iridium and rhodium complexes. Two classes of ruthenium complexes with sulfur-donor ligands have been prepared. The first class incorporates the ruthenium bis-bipyridine moiety while the second contains pentamethylcyclopentadienyl ruthenium. Most complexes synthesised exhibited reversible oxidation waves in the region of -0.1 to 0.2 V vs. Ag/Ag⁺. Their possible use as redox mediators was hindered by several factors, particularly difficulties in purification. They also exhibited oxygen sensitivity and low stability when in solution.The second area covered in this thesis is to further understand the bonding of the ligands used in the above study. A series of pentamethylcyclopentadienyl iridium and rhodium complexes were synthesised with three different dithiolato ligands. Two of the three ligands studies produced structures that included more than one metal centre leading to straining of the ligand. In order to study the monomeric form, the clusters were opened with a neutral phosphine ligand. Both the Ir…S and Rh…S bond lengths of all the complexes were within expected parameters.

Distinctive fine-structure due to ³⁵Cl/³⁷Cl isotopologue and isotopomer effects is resolved at high magnetic fields for ¹⁹⁵Pt and ¹⁰³Rh NMR signals, resulting in a unique NMR “finger-print”, with which it is possible to uniquely identify all chlorido containing Pt(IV) and Rh(III) complexes. In this study, these isotope shifts are computed from first principles in order to provide a solid theoretical framework for the empirical observations. Use is made of DFT to calculate the ³⁵/³⁷Cl and ¹⁶/¹⁸O induced isotope shifts in the ¹⁹⁵Pt NMR spectra of [Pt³⁵Cl₆]²⁻ and [Pt³⁷Cl₆]²⁻, for the [Pt³⁵Cl n ³⁷Cl₅₋ n(H₂O)]⁻ (n=0-5), cis-Pt³⁵Cln³⁷Cl₍₄₋n₎(H₂O)₂ (n=0-4), and fac-[Pt³⁵Cl n³⁷Cl₍₃₋ n₎(H₂O)₃]⁺ (n=0-3) series. The computational protocol is extended to calculate the ³⁵/³⁷Cl and ¹⁶/¹⁸O induced isotope shifts in [Pt³⁵Cl n³⁷Cl₍₅₋ n₎(OH)]²⁻ (n=0-5), cis- [Pt³⁵Cln³⁷Cl₍₄₋ n₎(OH)₂]²⁻ (n=0-4), fac-[Pt³⁵Cln³⁷Cl₍₃₋ n₎(OH)₃] ²⁻ (n=0-3), cis- [Pt³⁵Cl n³⁷Cl₂₋n(OH)₄]²⁻ (n=0-2) and [Pt³⁵Cl n³⁷Cl₍₁₋ n₎(OH)₅]²⁻ (n=0-1). For Rh(III), the ³⁵Cl/³⁷Cl isotope shifts in the ¹⁰³Rh NMR spectra of [Rh³⁵Cl n³⁷Cl₅₋ n(H₂O)] ²⁻ (n=0-5), cis-[Rh³⁵Cl n³⁷Cl₍₄₋ n₎(H₂O)₂]⁻ (n=0-4), and fac-Rh³⁵Cl n³⁷Cl₍₃₋ n₎(H₂O)₃ (n=0-3) were calculated. The ¹⁹⁵Pt and ¹⁰³Rh NMR chemical shifts computed for these species reproduce the order of magnitude of the observed effect reasonably well, up to ca. 1 ppm. In most cases, general trends are also captured qualitatively, thus providing the first theoretical basis for the origin of subtle isotope shifts in ¹⁹⁵Pt NMR spectra. Neither simple polarizable continuum models nor small, microsolvated complexes lead to improved isotope shifts for the series investigated, however, valuable insight into the degree of solvent interaction was gained. Using the polarized continuum model to calculate shielding/bond-length derivatives together with gas-phase zero-point corrections to estimate shieldings, it was shown that the contraction of the coordination sphere in the hydroxide complexes cause the Pt-Cl bonds to become magnetically equivalent, justifying why their isotopomers aren't resolved. In this study, theoretical modelling of structural effects on NMR parameters extends to the smallest scale, distance changes of a few femtometers upon isotopic substitution.

This thesis details the synthesis of novel Rh(I) and Rh(III) bis-phosphine fragments, and their use, along with other known rhodium species, to investigate the reactivity of amine-boranes, with a particular focus on the dehydrocoupling of the secondary amine-borane H3B.NMe2H (DMAB). Chapter 2 utilises the new mixed phosphine, PtBuiBu2, to investigate the role of the phosphine with regard to the corresponding low-coordinate organometallic species isolated. Their coordination and reactivity with amine-boranes is studied, leading to the development of a mechanism for an alkene hydroboration catalyst that employs H3B.NMe3 (TMAB). The final section of the chapter studies several fluxional processes pertinent to rhodium and iridium complexes of the model amine-borane TMAB using H/D exchange and low temperature NMR experiments. In Chapter 3, the mechanism of dehydrocoupling of DMAB is investigated in detail, employing catalysts based on the cationic bis¬-phosphine Rh fragment, {Rh(PCy3)2Ln}+. A series of stoichiometric and catalytic reactions are probed using NMR spectroscopy and mass spectrometry, revealing a complex mechanistic landscape. Subtleties include: the product of dehydrocoupling, [H2BNMe2]2, acting in an autocatalytic role; and parallel dehydrogenation of DMAB by a neutral catalyst present in a low but constant concentration. The mechanism was additionally interrogated through kinetic simulations conducted by Prof. Guy C. Lloyd-Jones (University of Bristol). From this, a generic mechanistic scheme has been suggested, aspects of which can be applied to transition metal and main group systems reported to catalyse the dehydrocoupling of DMAB. The final chapter moves on from cationic rhodium fragments to investigate the reactivity of the neutral rhodium species, Rh(H)2(PCy3)2Cl and [Rh(PCy3)2Cl]2, with amine-boranes. The mechanism by which Rh(H)2(PCy3)2Cl catalyses the dehydrogenation of DMAB has been investigated through initial rate and H/D exchange experiments, leading to the proposal of a reaction scheme. Additionally, the formation and characterisation of a base-stabilised boryl species has been reported resulting from the reactivity of an amino-borane with [Rh(PCy3)2Cl]2.

The functionalisation of C-H bonds has been widely studied in organic synthesis. This work presents the results of investigation into two areas of current research, copper-catalysed aromatic C-H functionalisation and rhodium-catalysed hydroacylation. Chapter 1 presents the development of palladium- and copper-catalysed aromatic C-H functionalisation with particular attention paid to regiocontrol. Chapter 2 describes the development of copper-catalysed cross-coupling of perfluorinated arenes and alkenyl halides along with efforts to expand this methodology to a more general reaction. In Chapter 3 the development of chelation-controlled rhodium-catalysed hydroacylation is discussed. Chapter 4 outlines the utilisation of amino acid derived N-methylthiomethyl aldehydes in rhodium-catalysed hydroacylation methodology.

This thesis explores the area of the intermolecular hydroacylation reaction, catalysed by rhodium diphosphine complexes. A range of latent low-coordinate rhodium diphosphine complexes have been synthesised, and their catalytic activity for the hydroacylation reaction has been investigated. In particular, emphasis has been placed on understanding how subtle changes in diphosphine steric properties affect, and can be used to control, selectivity of this catalysis. Chapter 2 presents investigations into rhodium complexes incorporating the potentially hemilabile P-O-P ligands: POP’, XANTphos and Xphos. The resulting complexes have been fully characterised and their activity for the catalytic intermolecular hydroacylation of aldehyde I (HCOC₂H₄SMe) and alkene II (H₂C=CHCO₂Me) established and compared to the DPEphos system. Further reactivity of Xphos for aromatic aldehyde V (HCOC₆H₄SMe) and alkene II, and aldehyde V and alkyne XI [HC≡CC₆H₃(CF₃)₂] has also been explored, and compared with the catalytic activity of {Rh(PPh₃)₂}⁺. Focus moved from potentially hemilabile ligands to chelating diphosphine ligands of the type PPh₂(CH₂)nPPh₂ (where n = 2-5), and then on to ortho-substituted bulky analogues of the type P(₀-C₆H₅R)₂(CH₂)₂P(₀-C₆H₅R)₂ (where R = Me and ⁱPr) complexed to rhodium. Chapter 3 outlines the complexes synthesised, and their activity for the catalytic intermolecular hydroacylation of aldehyde I and alkene II, aromatic aldehyde V and alkene II or aldehyde V and alkyne XI. Possible explanations for the observed switch in selectivity from alkene to aldehyde hydroacylation, and linear alkyne to branched alkyne hydroacylation, have been explored and are detailed. The final chapter concerns the structure of an interesting catalytic intermediate: the branched alkenyl species for the {Rh(DPEphos)}+ catalysed hydroacylation of aldehyde V and alkyne XI. Investigations into the kinetic and catalytic behaviour of this system were carried out, and a reaction scheme has been proposed which correlates well with kinetic modelling undertaken by Prof. Guy Lloyd-Jones of the University of Bristol.

Chapter 1 is an overview of the key developments in rhodium-catalysed hydroacylation. The main focus of this chapter is the use of various chelation strategies for the stabilisation of key rhodium-acyl intermediates. In addition, the more recent emergence of regioselective hydroacylation processes has been highlighted. Chapter 2 discloses the branched-selective intermolecular hydroacylation of 1,3-dienes and S-chelating aldehydes to afford synthetically useful 1,5-dione products. The evaluation of a number of different phosphine ligands for this process identifies a correlation between ligand bite angle and reaction regioselectivity. Chapter 3 discusses the development of a linear-selective hydroacylation process for previously challenging alkyne substrates. This, in combination with a complementary branched-selective process, provides a ligand-controlled regioselectivity switch between the branched and linear pathways. Finally, Chapter 4 details efforts towards the development of multicomponent, tandem processes through exploitation of our synthetically useful branched hydroacylation adducts.

By examining structure activity relationships for a given catalytic reaction it is possible to discover what ligand features and parameters lead to stable and highly active/selective catalyst systems. With this knowledge in hand it may be possible to rationally design next generation ligands and catalysts to affect improved substrate transformations, with higher selectivities and faster reaction times. The success of Burk's DuPhos ligands in asymmetric hydrogenation demonstrated that chiral phosphacycles can be a potent source of chiral induction, whilst in a similar vein the work of van Leeuwen and Kamer established the wide bite angle xanthene based ligands as excellent catalysts in a range of reactions including hydroformylation. In a preliminary study with Osborne they showed that combining these wide bite angle ligand backbones with Burk's phospholane moieties led to a new powerful ligand in asymmetric allylic substitution. To examine the potential of combining these two ligand features further we designed and synthesised nine new C2-symmetric bidentate wide bite angle bisphosphacyclic ligands, featuring phosphetane, phospholane or diazaphospholane rings, aiming at a wide diversity of steric and electronic properties. The application of these ligands as chiral auxiliaries in transition metal catalysed reactions, including; hydrogenation, hydrocyanation, hydroformylation and allylic alkylation has been investigated. Good to excellent enantioselectivities were observed in all reactions, with maximum ee's of 92.5% observed in hydrogenation, using N-(3,4-dihydro-1-napthalenyl)-acetamide as substrate, and of 96.2% in the alkylation of 1,3-diphenyl-2-propenyl acetate.

Highly stereo- and regioselective rhodium-catalysed carbometallations of ynamides using organometallic reagents have been disclosed. The scope of the process was explored, and investigations revealed that Rh(cod)(acac) acts as an effective precatalyst for carbometallation of ynamides using a range of organozinc reagents. A plausible mechanism has been suggested where an alkenylzinc intermediate is formed. This species has been exploited in further transformations with electrophiles and in cross-coupling reactions, thus providing access to multisubstituted enamides in a stereo- and regioselective manner. It was also possible to carry out the carbometallation of ynamides using organoboron reagents by using [Rh(cod)(MeCN)2]BF4 as a precatalyst. This complementary protocol allowed the introduction of a greater diversity of substituents, including those carrying sensitive functional groups. Mechanistic studies, including deuterium labelling, suggested that an alkenylrhodium intermediate was produced during the course of the reaction. With a set of optimised conditions, this species was successfully used in a tandem carbometallation– conjugate addition (or annulation) reaction with bifunctional arylboron reagents. The 2-amidoindene products were obtained in good yields and high regioselectivities. Preliminary studies on the development of an asymmetric variant of this transformation have been undertaken and the initial results have been reported. In addition, highly enantioselective dihydroxylation of the enamide substrates prepared from the developed rhodium-catalysed carbometallations of ynamides was readily accomplished using commercially available AD-mix- . This novel procedure provides an access to a wide range of chiral products that might be difficult to access using existing methods. Finally, as a further exemplification of asymmetric enamide dihydroxylation, this method was applied to a concise total synthesis of the antifugal natural product (+)-Tanikolide.

A series of cationic Rh(I) diphosphine and phosphine-alkene complexes have been isolated and fully characterised. The reactivity of these species towards hydrogenation, dehydrogenation and dehydrocoupling reactions has been investigated. The use of potentially hemilabile ligands DPEphos and XANTphos in the intramolecular dehydrogenation chemistry of tricyclopentylphosphine is reported. The comparison in reactivity of these isolated diphosphine phosphine-alkene complexes towards hydrogenation and with acetonitrile is discussed along with their ability to dehydrocouple secondary silane, Ph₂SiH₂, and amine-borane H₃B·NMe₂H. The acceptorless dehydrogenation of a tethered cyclopentane with cationic Rh(I) diphosphine complexes has also been extended to include thioethers. Isolated cationic Rh(I) phosphine-alkene complexes with labile fluorobenzene ligands are found to act as a source of the reactive 12-electron [Rh{PR₂(ƞ²-C₅H₇)}]+ (R = cyclopentyl (Cyp)/ iPr) fragment in solution and can coordinate two amine-borane ligands (either H₃B·NMe₃, H₃B·NMe₂H or H₃B·NMeH₂) in a novel and unique bis-σ-binding mode. The catalytic activity of some of these isolated complexes in the dehydrocoupling of H₃B·NMe₂H and H₃B·NMeH₂ has been determined. With a view to further understanding the mechanism of catalytic transition metal assisted amine-borane dehydrogenation and dehydrocoupling, known B-N intermediates H₃B·NMe₂BH₂·NMe₂H and [H₂B·NMeH]₃ were also coordinated to the [Rh{PCyp₂(ƞ²-C₅H₇)}]+ fragment and investigated with regard to their role in the catalytic cycle. Structure activity relationships determined from stoichiometric reactions of cationic Rh(I) diphosphine fluorobenzene complexes with amine-boranes enabled the design of a highly efficient homogeneous catalyst capable of dehydrogenating H₃B·NMe₂H to [H₂BNMe₂]₂ at 0.2 mol% loading in 30 minutes at 298 K. Rapid dehydrogenation and dehydrocoupling of H₃B·NMeH₂ to form high molecular weight poly(N-methylaminoborane) with a low PDI has also been achieved. Investigations using model aminoborane H₂B=NiPr₂ and intermediate B-N species H₃B·NMe₂BH₂·NMe₂H and [H₂B·NMeH]₃ has helped establish an overall mechanistic rationale for this process.

Rhodium-catalysed hydroacylation provides a highly atom economic synthesis of ketone products from the combination of aldehydes and multiple bond systems by C-H bond activation. This work evaluates the combination of intermolecular hydroacylation for the synthesis of classical heterocycle precursors and their dehydrative cyclisation to give rise to a range of substituted heterocyclic compounds. Chapter 1 outlines recent developments in the chemistry of hydroacylation. Particular attention is paid to the various chelation strategies employed in intermolecular hydroacylation. Chapter 2 discusses some relevant and recent developments in the field of pyridine and pyrrole synthesis. Having established that β-sulphur chelation controlled hydroacylation can be used to synthesise pyridines in Chapter 3; attention was turned to hydroacylation of propargyl amines in Chapter 4. The methodology was expanded to provide a synthesis of γ-amino enones. The hydroacylation reaction and cyclisation is combined in a procedure that utilises thermal Boc-deprotection and cyclisation to give a range of highly-substituted pyrroles. The regioselectivity of the hydroacylation of propargyl amines is investigated in Chapter 5 by application of statistical Design of Experiments methodology. Optimised conditions were identified with minor improvements in the selectivity of the reaction.

This work describes the extension of rhodium-catalysed intermolecular hydroacylation to encompass some tandem catalytic processes, wherein a further catalytic process is enacted on the product of an intermolecular hydroacylation reaction in “one pot”. Chapter 1 entails an overview of the development of hydroacylation chemistry, with a focus on the different types of catalytic systems which have been used to facilitate this transformation. A brief description of some precedented examples of tandem catalytic processes which include a hydroacylation reaction is also included. Chapter 2 describes the intermolecular hydroacylation of chelating aldehydes and propargylic alkynes to form γ-hydroxy-α,β-enones, and their subsequent acid-catalysed cyclisation to form substituted furans in a "one-pot" procedure. Additionally, a tandem intermolecular hydroacylation/double-bond isomerisation protocol for the synthesis of 1,4-dicarbonyl compounds is detailed, and the subsequent transformation of this class of compounds to heterocycles is included. Chapter 3 focuses on the development of tandem catalytic hydroacylation/reductive processes, wherein a hydroacylation product undergoes a reduction which is catalysed by the hydroacylation catalyst. Chapter 4 describes an attempt to utilise the rhodium-catalysed conjugate addition of arylmetal species to enomes to create a tandem alkyne hydroacylation/conjugate addition process. Chapter 5 encompasses the use of a small range of different solvents in rhodium-catalysed hydroacylation, in an attempt to find higher-boiling alternatives to acetone and a "green" alternative to the commonly used DCE.

This thesis describes the synthesis and reactivity of previously unprecedented bicyclic methylene aziridines via rhodium(II) catalysed cyclisation of α-allenic N-tosyloxycarbamates. These aziridines undergo reaction with organocuprates to give cis- disubstituted oxazolidinones by nucleophillic attack at the vinylic centre; plausible mechanisms for this process are discussed. Similar rhodium(II) catalysed cyclisations of β-allenic sulfamates afford cyclic enamines, aminocyclopropanes or bicyclic methylene aziridines; the product ratio depends on the allene substitution pattern. Suitably-designed substrates undergo trapping of the proposed intermediate amino allyl cation by internal nucleophiles or by cycloaddition. Finally, thermally-induced intramolecular cycloadditions of γ-allenic azides are described that give triazolines or [1,2,3]-triazoles.

Very little information exists on the marine biogeochemistry of Rh, Pd and Pt, or the platinum group elements (PGE), an emerging group of contaminants whose principal emissions are associated with the abrasion of the catalytic converter in motor vehicles and chemotherapy drugs discharged in hospital wastes. In this study, Rh(III), Pd(II) and Pt(IV) were added individually and in combination to cultures of the marine microalga, Chlorella stigmatophora, maintained in coastal seawater at 15oC and under fluorescence lighting both in the presence and absence of trace nutrients (e.g. Fe, Co, Zn and EDTA). The accumulation of PGE was established under varying conditions (pH, algal biomass, PGE concentration, time) by ICP-MS analysis of seawater and nitric acid digests and EDTA washes of the alga, the latter giving a measure of PGE adsorption by C. stigmatophora. Under all conditions the extent of accumulation was in the order: Rh > Pd >> Pt. In short-term (24-h) exposures, accumulation isotherms were quasi-linear up to PGE concentrations of 30 ug L-1, although Pd displayed convexity, hence saturation of available binding sites, at greater concentrations. The pH, adjusted between about 5.5 and 9.5 by addition of acid or base, did not have a great impact on PGE accumulation, with Rh displaying a moderate increase in accumulation and Pd a moderate reduction with increasing pH. More important, all PGE displayed a significant reduction in accumulation on a weight-normalized basis with increasing concentration of algae, an effect not reported for metal-marine algal interactions previously in the literature. Longer-term experiments showed that the rates of both overall accumulation and internalization were greatest for Pd and least for Pt. Consistent with this observation, the toxicity to C. stigmatophora evaluated by both pigment content and growth rate, was significantly greater for Pd than for Pt. Differences in the biogeochemical behaviours among the PGE are attributed to differences in their aqueous speciation in seawater, different affinities for the algal surface, different tendencies to cross the cell membrane, and especially with regard to Pd and Pt, differences in the rates of these interactions. Thus, although the equilibrium chemistries of Pd and Pt are very similar, their differential biogeochemistries are the result of kinetic constraints on reactions involving the latter. Because the environmental concentrations of PGE are predicted to increase with increasing emissions from vehicles and hospitals, the results of this study make an important contribution to an improved understanding of the likely effects and fates of these emerging contaminants in the marine environment. The results are also more generally important to an improved understanding of the interactions of trace metals with microalgae in seawater.

Aqueous-biphasic organometallic catalysis is, as illustrated by the industrial hydroformylation of propene and butene, one of the most promising ways to overcome the intrinsic problem of catalyst separation in organometallic catalysis. However, for poorly water-soluble substrates, mass transfer limitations bring the reaction rate below any that could be economically viable, greatly limiting the scope of this elegant technology. We have studied three different strategies to overcome this limitation. We developed additives that speed up the reaction whilst retaining fast phase separation and good metal retention. Evidence suggests that those additives affect the reaction by forming emulsions with poor stability under the reaction conditions These emulsions increase the interfacial surface area but break after settling for a short time. We also developed ligands that allow the catalyst to be reversibly transported between an aqueous and an organic phase upon addition and removal of carbon dioxide. This allows the reaction to be carried out under homogeneous conditions, only limited by intrinsic kinetics, and the catalyst to be separated by aqueous extraction triggered by carbon dioxide. The catalyst can be returned to a fresh organic phase by flushing out the carbon dioxide. By applying this methodology for the hydroformylation of medium chain length alkenes, very high reaction rates were obtained and the catalyst could be recycle three times with excellent retention of activity and low metal leaching. This methodology could also be reversed with the reaction being carried out in an aqueous phase in the presence of carbon dioxide and extracting the catalyst into an organic solvent using nitrogen flushing. Finally, we briefly investigated the use of an oscillatory baffled reactor as a mean for mass transfer improvement for aqueous-biphasic hydroformylation. This new type reactor did not improve the performance of the system under the investigated conditions, but may require less energy input for equivalent agitation and mixing.

The research presented herein is concerned with the exploration of rhodium-catalysed addition reactions with organoboranes encompassing the 1,4-addition enolate protonation to benzyl acrylate esters, and the synthesis of chiral organoboranes for use in the synthesis of natural products Hermitamides A and B. Chapter 1 introduces the area of rhodium-catalysed conjugate addition as a tool for asymmetric synthesis. An extensive discussion of this methodology is included and recent advances in the area will be highlighted. In addition to this some recently published alternatives to organoboranes are outlined and their use in rhodium-catalysed chemistry documented. Chapter 2 discusses the tandem process of rhodium-catalysed conjugate addition enolate protonation, a recently observed asymmetric development. By using a novel route to benzyl acrylic esters the synthesis of α,α′-dibenzyl esters is achieved in excellent yields and selectivity. This study highlights the fact that when dealing with 1,1-disubstituted activated alkenes it is more difficult to produce enantioselective results as the chirality is determined in the protonation step and not during insertion. Some insights into the mechanism are proposed based on the outcomes observed. Chapter 3 describes the total synthesis of Lyngbic Acid and related structures Hermitamides A and B. Synthesis of these natural products are achieved by synthesis of an enantiopure organoborane species and its subsequent coupling via rhodium catalysis. Some interesting insights into the addition of alkenyl organoborane species to unsubstituted 1,1-activated alkenes are detailed. Chapter 4 describes the synthesis and characterisation for the compounds discussed in the previous chapters.

The carbonylation of methanol to acetic acid is one of the most important applications in homogeneous catalysis. The first chapter comprises a review on the mechanistic studies into the catalytic cycle of the ‘Monsanto process’ and includes some of the most prominent studies into the use of phosphines in the rhodium-catalysed carbonylation of methanol. The second chapter of this thesis reports on an investigation into the application of rhodium complexes containing several C4 bridged diphosphines, namely BINAP, dppb, dppx and dcpb as catalysts for hydrogen tolerant methanol carbonylation. An investigation into the structure, reactivity and stability of pre-catalysts and catalyst resting states of these complexes has also been carried out. The origin of this hydrogen tolerance is explained based on the differing reactivities of the Rh acetyls with hydrogen gas, and by considering the structure of the complexes. In the third chapter I report on an investigation into how electronic properties and coordination mode affect the elimination of phosphonium salts from rhodium complexes. The stability of a range of monodentate, bidentate and tridentate rhodium-phosphine complexes was tested. I also report on the formation of a novel bidentate complex containing a partially quaternised TRIPHOS ligand and investigate the mechanism of formation using 13CH3I. Strong evidence is also presented supporting a dissociative mechanism as the means of phosphine loss from the rhodium centre. In the final chapters I report an investigation into the stability of rhodium-aminophosphine ligand complexes and into increasing the solubility of potential rhodium pre-catalysts through the use of amine-containing phosphine ligands.

This thesis describes the synthesis of novel ligands that include enantiomerically pure acetal and oxazoline moieties. These ligands are utilised in a number of metalmediated asymmetric syntheses. All asymmetric acetals and pyridine based acetals are synthesised in good yield in a single step from their corresponding enantiomerically pure diols. C2 symmetric bisacetals are investigated as ligands in the organolithium and Grignard additions to benzaldehyde with promising results. C2 symmetric bisacetals and pyridine based acetals are tested for their ability to induce asymmetry in copper(l) catalysed cyclopropanation of styrene using ethyl diazoacetate and the lanthanide(lII) catalysed Diels-Alder cycloaddition involving Danishefsky's diene with little success. Enantiomerically pure phosphinooxazoline ligands are available in good yield in two steps from their corresponding enantiomerically pure aminoalcohols. Enantiomerically pure acetal substituted pyridines and phosphinooxazoline ligands are considered in the rhodium (I) catalysed hydrosilylation of ketones. Reaction conditions for the more successful phosphinooxazoline ligands are optimised. Using these ligands a range of enantiomerically enriched alcohols is presented in good yield and enantiomeric excess. Novel phosphinooxazoline ligands are applied to the palladium(O) catalysed allylic substitution reaction with excellent enantioselectivities of the substitution product.

(Cp*₂)Sm(THF)₂ (CP* = 1,2,3,4,5-pentamethylcyclopentadienyl) was prepared and applied to the hydroamination/cyclization of unsaturated amines. Enantiomerically pure C₂-symmetric ligand Cp', (Cp' = 8,10-diophenyltricyclo[5.2.2.0²,⁶]undeca-2,5-dienyl) was reacted with SmI₂(THF)₂ to form an organolanthanide complex (Cp'₂)Sm(THF)₂ which unfortunately did not catalyze the hydroamination/cyclization reaction of unsaturated amines. One suggestion we can give to account for the lack of activity of the organosamarium catalyst, is that the complex is formed as a hydride bridged dimer. Attempts to characterize the organosamarium species were not successful due to the extreme air sensitivity of the complex. Experimental inferences and observations made while carrying out the organolanthanide experiments allow us to be confident that (Cp'₂)Sm(THF)₂ was synthesized. Mixed and bis(cyclopentadienyl)titanium complexes containing C₂-symmetric ligands Cp' and Cp'' (Cp'' = 8,10-dicyclohexyltricyclo[5.2.2.0²,⁶]undeca-2,5-dineyl) have been made and used in hydrogenation and hydrosilylation reactions. Good enantioselectivities were obtained for the bis complexes but the steric hindrance of the bulky ligands limited the type of substrate that could react. The mixed (η⁵-C₅H₅)(η⁵-Cp'')TiCl₂ complex gave a low e.e. for the hydrogenation of 2-phenyl-1-butene. We believe problems activating the titanocene complexes with n-BuLi, were the reason for the hydrogenation of imines and enamines being unsuccessful. (Cp')₂ZrCl₂ has been prepared and used in the hydrogenation of 2-phenyl-1-butene. This complex gave the highest e.e. result, at room temperature, for any organotransition metal catalyzed hydrogenation of this challenging substrate. Unfortunately the complex was too sterically bulky to perform ethylmagnesiation reactions. The mixed (η⁵-C₅H₅)(η⁵Cp'')ZrCl₂ complex was prepared in good yield, but gave poor e.e.s. in the hydrogenation of 2-phenyl-1-butene. We were pleased to find that the mixed zirconocene complex catalyzed ethylmagnesiation reactions of N-allylaniline and allyl-phenylsulphide successfully, although the enantioselectivities were low.

The results of an effective core potential ab initio and Density Functional Theory (DFT) quantum mechanical study of the rhodium- and iodide- catalysed Monsanto acetic acid cycle are presented. The geometries and energetics of the intermediates and transition states have been determined for the key steps of the cycle. The potential influence of variables such as solvent and ligands, and the controlling electronic structure features have been examined. Theoretical data for the analogous iridium system are also reported. The lowest energy transition state determined at the restricted Hartree-Fock (RHF) level for the oxidative addition Of C1131 to CiS-[M(CO)2121- (M=Rh, Ir) is a "linear" structure, involving classical SN2 back- side attack by the transition metal. Secondary a-Deuterium kinetic isotope effects calculated for this mechanism are in excellent agreement with experiment. Both electron correlation and an electrostatic medium have a significant influence on the nucleophilic substitution reaction energetics. Second-order Moller-Plesset theory (MP2) calculations, with the effect of solvent included, using the self-consistent reaction field (SCRF) model, predict activation barriers in good agreement with experiment. The overall oxidative addition process is found to be exothermic at the MP2 level for both metal systems, but more so for iridium. The transition state and intrinsic reaction co-ordinate (IRC) calculated for migratory insertion in [CH3M(CO)2131- (M=Rh, Ir), indicate that the reaction proceeds via a concerted movement of CH3 and CO groups toward each other. In the rhodium system this reaction is predicted to take place with a low activation barrier and lead to exothermic formation of a five co-ordinate acyl complex in agreement with experiment. By contrast, migratory insertion in the iridium system has a high barrier and is endothermic. Analyses suggest that the difference in reactivity of rhodium and iridium complexes can be correlated to the greater strength of metal-carbon bonds for the heavier transition metal. DFT calculations of the strongly bound ground state complexes yield geometrical structures and carbonyl vibrational frequencies which are comparable, or superior, to those obtained at the RHF and MP2 levels in the same Gaussian basis. However, calculations of the transition states and reaction co-ordinates have not been successful. It is proposed that the currently used functionals are not suitable for the calculation of transition states when weak interactions become important.